The present invention concerns an apparatus for transporting envelope blanks in an envelope making machine. In this specification the term envelopes is used to denote envelopes for containing letters and like documents and also shipping bags and the like.
In a typical envelope making machine, envelope blanks or stampings are transported through various, successively arranged stations, for implementing various production steps therein. By way of example, the envelope blanks may typically pass through a printing station, a window glueing-in station for inserting and glueing a window in position in the envelope blank, a side flap folding station, a bottom flap folding station and a drying station.
One form of an apparatus for transporting envelope blanks in the side flap folding station of an envelope making machine can be found in EP 0 502 687 A1. In that case, the envelope blanks are transported by means of a plurality of endless belts or bands which are arranged in side-by-side relationship at a mutual spacing. Ambient air is drawn through the resulting intermediate spaces thereby defined between the endless belts, into a suction or vacuum chamber disposed beneath the plane of transportation movement defined by the endless belts. In that way, the envelope blanks are retained in a stable position on the endless belts so that they cannot be shifted or turned by the forces which occur in the side flap folding procedure. A disadvantage in this respect is that, when dealing with smaller formats of envelopes to be produced, the outer regions of the movable suction support formed by the endless belts and the spaces therebetween are not put to use so that ambient air is unnecessarily drawn in through the intermediate spaces between the endless belts. That results in unnecessary power consumption on the part of the suction blower used.
A further form of apparatus for transporting envelope blanks in a side flap folding station is to be found in U.S. Pat. No. 3,288,037. In that apparatus, the envelope blanks are conveyed through the side flap folding station on a single conveyor belt which has a plurality of perforation holes therethrough. Disposed beneath the conveyor belt is a suction chamber by means of which ambient air can be drawn through the perforation holes. In that way the envelope blanks are also retained on the conveyor belt in a stable position by means of the effect of suction air applied thereto. FIG. 1 of U.S. Pat. No. 3,288,037 to which reference may be made shows that the envelope blank or the envelope to be produced projects beyond the edges of the conveyor belt, being the lateral edges in the direction of movement of the conveyor belt. Therefore, the regions of the envelope blank which project beyond the edges of the conveyor belt are not supported by the conveyor belt itself, but by other support elements which are disposed beneath those regions. Unwanted frictional forces occur between the stationary support elements and the envelope blanks by virtue of the relative movement of the envelope blanks with respect to the support elements. Those frictional forces have a particularly detrimental effect in the production of what are known as side closure shipping bags which have a comparatively large side flap and a comparatively small side flap which are not folded over simultaneously but in succession. By virtue of the frictional forces which occur asymmetrically as a result, between the support elements and the regions of the envelope blanks which project beyond the conveyor belt, turning moments occur about the vertical axis of the envelope blanks and can undesirably tilt or turn the envelope blanks. Such turning moments are referred to herein as yawing moments. Unwanted frictional forces or yawing moments can also be produced in other processing stations of the envelope making machine.
An object of the present invention is to provide an apparatus for transporting envelope blanks in an envelope making machine, which makes optimum use of the suction power of the suction fan and which at the same time at least substantially contributes to preventing the occurrence of unwanted frictional forces and/or yawing moments at the envelope blanks.
Another object of the invention is to provide an apparatus for transporting envelope blanks through an envelope making machine, which affords greater versatility in terms of adaptability of the operating structure of the apparatus to varying envelope formats.
Yet another object of the present invention is to provide an apparatus for transporting envelope blanks through an envelope making machine, which is so designed as to make optimum use of a suction effect applied to envelope blanks by means of a suction chamber to hold them in position as they pass through the machine.
Still a further object of the invention is to provide an envelope making machine including an apparatus for transporting envelope blanks therethrough in a more efficient and more reliable fashion while being of a simplified operating structure.
In accordance with the principles of the present invention the foregoing and other objects are attained by an apparatus for transporting envelope blanks in an envelope making machine, comprising at least one conveyor belt having a plurality of perforation holes, for transporting thereon the envelope blanks in a direction of movement in a transport plane defined by the conveyor belt. At least one suction chamber is disposed beneath the conveyor belt, operable to draw ambient air through the perforation holes. Provided beside the conveyor belt at least one of the two sides thereof is at least one guide belt. The conveyor belt and the one or more guide belts are drivable in such a way that they move synchronously in the direction of movement of the blanks through the apparatus.
It will be noted in this respect that the suction chamber is of such an arrangement, configuration and dimensions that a suction action for holding the envelope blanks in place on the at least one conveyor belt is produced exclusively above the conveyor belt, while the space above the at least one guide belt does not have any suction action operable thereat to draw the envelope blanks on to the guide belt.
Further in accordance with the principles of the invention the foregoing and other objects are attained by an envelope making machine including an apparatus for transporting envelope blanks therethrough, comprising at least one conveyor belt having a plurality of perforation holes and operable to transport thereon the envelope blanks through the machine. At least one suction chamber is disposed beneath the conveyor belt, operable to produce a suction effect to draw ambient air through the perforation holes downwardly through the conveyor belt. At least one guide belt is disposed beside the conveyor belt on at least one of the two sides thereof. The conveyor belt and the at least one guide belt are driven in such a way that they move synchronously to convey envelope blanks through the machine.
As will be apparent from the description hereinafter of a preferred embodiment of the envelope blank-transporting apparatus, the apparatus affords the advantage that the width of the perforated conveyor belt can be designed to conform to the width of the smallest envelope format which is to be produced with the envelope making machine in which the apparatus of the invention is used. That ensures that no unnecessary ambient air is drawn in even through the perforation holes which are in the outer regions of the conveyor belt, and accordingly the suction power of the suction chamber and the suction fan producing the suction flow is not wasted. The apparatus according to the invention also involves a minimum amount of complication and expenditure in terms of changing envelope formats. In that respect, essentially only the respective tool elements of the respective station in the machine have to be displaced transversely with respect to the direction of movement of the envelope blanks through the apparatus. For example, in the case of a side flap folding station in an envelope making machine, the folding elements are moved closer together or are moved further away from each other, in order to adapt the folding station to differing formats.
In accordance with a preferred feature of the invention, it is possible to provide at least one or more guide belts on both sides of the conveyor belt. It is however also possible to arrange one or more such guide belts only on one side of the conveyor belt. That may be the case for example when, in a given part of the side flap folding station, a large side flap of a side closure shipping bag is folded while no processing or folding operation is carried out on the shipping bag in that part of the station, on the side where the small side flap is disposed.
Preferably, the conveyor belt and the at least one guide belt are driven by the same drive device. That is the best manner of ensuring that the conveyor belt and the guide belts are moved synchronously, that is to say at the same speed, in the passage direction through the apparatus. It is also possible in accordance with the invention however to provide a respective separate drive device for the conveyor belt and for the at least one guide belt, as long as they are suitably matched to each other in such a way that the conveyor and guide belts move synchronously relative to each other.
A stationary separating bar or rail can advantageously be provided between the conveyor belt and the at least one guide belt. The separating bar separates the conveyor belt from the guide belt or belts and in addition ensures that ambient air is not sucked in by way of the lateral edges of the conveyor belt.
In a preferred feature of the invention, a fault or incident detection sensor is disposed in the separating bar. The sensor may be an electromagnetic or optical sensor integrated into the separating bar. In that case for example a photodiode may be integrated into the separating bar, to receive optical signals constantly or at intervals of time from a photoemitter disposed above the transport plane. In fault-free operation of the envelope making machine the fault detection sensor records regular signal interruption times in optical transmission of the signals, which are caused by the envelope blanks passing therethrough and which are thus characteristic in respect of trouble-free operation. If however the sensor detects irregularities in the signal interruption times, it can signal for example to a central machine control system that the envelope making machine is suffering from an operational fault which is characterised by such irregularities.
A further advantage of the separating bar or bars is that, in the direction of movement of the envelope blanks through the apparatus, the bar or bars can be prolonged a little beyond a drive roller or shaft for the conveyor and guide belts which are in the form of endless belt members. That provides that the envelope blanks are reliably transferred to the next part in the same station or to the next station of the envelope making machine. Otherwise, the envelope blanks could remain clinging to the conveyor belt or the guide belts, for example due to a static charge, and as a consequence could undesirably follow those belts in their movement as they pass around the drive roller or shaft. The fact that the separating bar or bars is or are prolonged in that way means that the envelope blanks are guided by the bars in such a way as to be peeled off the belts as they move, thereby to ensure that the envelope blanks are not deflected out of their substantially straight path of movement through the apparatus.
In accordance with a further preferred feature of the invention, the apparatus may have two or more perforated conveyor belts. In order to ensure that such a construction does not suffer from a low level of efficiency at each of the plurality of conveyor belts, in terms of making use of the suction effect generated by the suction chamber, stationary sealing bars are arranged in the intermediate spaces between the conveyor belts. The sealing bars ensure that ambient air cannot be drawn through the intermediate spaces between the conveyor belts. If required, the sealing bars can also be prolonged in the direction of movement of the envelope blanks through the apparatus, in order to produce a peeling-off effect, in a similar manner to the above-described prolongation of the separating bars.
It is also possible for an electromagnetic or optical fault detection sensor as described above to be integrated into one or more of the sealing bars. It will be appreciated that the apparatus according to the invention can be used in any station which is usually provided in an envelope making machine. In particular, the apparatus can also operate as a pure transportation station defining a transport plane, above which no processing operations are implemented on the envelope blanks. Examples in regard to possible uses of the apparatus according to the invention are in a side flap folding station, a window glueing-in station or a drying station.
Further objects, features and advantages of the invention will be apparent from the description hereinafter of a preferred embodiment of the invention.